Atmospheric Entropy. Part I: Climate Dissipation Structure

Abstract

Atmospheric entropy and its association with climate dissipation are investigated. The balance equation for entropy is derived through the mean and transient thermal and moisture equations. The entropy production contains the internal and external parts. The external entropy production, due to small-scale diabatic heating, can be evaluated by the surface entropy flux. Using NCEP data from 1998 to 2007, it is found that the surface entropy flux is much larger in the tropics than in the extratropics. In the December–February (DJF) Northern Hemisphere, there are two strong positive centers of boundary layer supply of entropy: one is in the northwestern Pacific and the other is in the western Atlantic. The external entropy production, due to large-scale eddy flow, can be evaluated by the convergence of eddy entropy flow. It is found that the large-scale eddy entropy flow is divergent in the midlatitudes and convergent in the higher latitudes. The internal entropy production shows the dissipation to the orderly thermal structure. For the internal entropy production due to a large-scale eddy, it is shown that in the Northern Hemisphere during DJF there are three maxima, located in the western Pacific, western Atlantic, and northern polar regions. This illustrates the dissipation of the highly organized thermal structure in such regions. An interesting finding is that the large-scale eddy internal entropy production is negative in the lower stratosphere. It is found that the long-time-averaged global mean of the internal entropy production is 0.037 49 W m−2 K−1. By including the entropy sink from radiation, the total entropy production is close to balance.